WDPN32 PGTW 102100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 17W (LINFA) WARNING
NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 17W (LINFA), LOCATED APPROXIMATELY 133 NM
EAST-SOUTHEAST OF DA NANG, VIETNAM, HAS TRACKED WESTWARD AT 18 KNOTS
(KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY REVEALS A CONSOLIDATING LOW LEVEL CIRCULATION CENTER (LLCC)
WITH DEEP CONVECTIVE BANDING WRAPPING INTO THE LLCC FROM THE NORTH
AND WEST. A 101740Z ATMS 88.2 GHZ MICROWAVE IMAGE DEPICTS DEEP
CONVECTIVE BANDING WRAPPING INTO THE WESTERN QUADRANT OF THE LLCC,
WHICH SUPPORTS THE INITIAL POSITION WITH GOOD CONFIDENCE. THE
INITIAL INTENSITY IS ASSESSED AT 40 KTS, HEDGED SLIGHTLY HIGHER THAN
A 101426Z ASCAT-C IMAGE SHOWING NUMEROUS 30-35 KNOT WINDS OVER THE
NORTHERN SEMICIRCLE BASED ON IMPROVING CONVECTIVE STRUCTURE AND
MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES OF T3.0 (45 KTS) BY
PGTW/RJTD. ENVIRONMENTAL ANALYSIS INDICATES LOW (<10 KT) VERTICAL
WIND SHEAR (VWS), DIFFLUENT FLOW ALOFT, AND CONDUCIVE SEA SURFACE
TEMPERATURES (SST) AT 29-30 CELSIUS. TS 17W IS TRACKING GENERALLY
WESTWARD UNDER THE STEERING INFLUENCE OF A SUBTROPICAL RIDGE (STR)
POSITIONED TO THE NORTH.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TS 17W WILL TRACK GENERALLY WESTWARD THROUGH THE REMAINDER OF
THE FORECAST PERIOD ALONG THE SOUTHERN PERIPHERY OF THE
AFOREMENTIONED LOW-LEVEL STR. TS 17W WILL STEADILY INTENSIFY TO A
PEAK OF 45 KTS BY TAU 12. THE SYSTEM SHOULD MAKE LANDFALL NEAR TAU
12 SOUTH OF DA NANG, VIETNAM. AFTERWARDS, TS 17W WILL TRACK
WESTWARD, WEAKENING DUE TO INCREASING VWS AND THE RUGGED TERRAIN OF
VIETNAM UNTIL DISSIPATION BY TAU 48. WITH THE EXCEPTION OF THE UKMET
ENSEMBLE MEAN SOLUTION, NUMERICAL MODEL GUIDANCE REMAINS IN GOOD
AGREEMENT THROUGHOUT THE FORECAST PERIOD WITH A 66 NM SPREAD AT TAU
24. THE JTWC FORECAST TRACK LIES NEAR THE MULTI-MODEL CONSENSUS AND
THE ECMWF MODEL SOLUTION WITH FAIR CONFIDENCE.//
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